The invention relates to the field of automotive electrical systems. Specifically, the invention is directed to a method of protecting the starter/alternator in an I.C. engine start-up sequence where the I.C. engine fails to start, and also to determine what type of fault condition is present.
A recent trend in automotive electrical systems is the combining of the formerly separately functioning and operating starter and alternator/generator components. As automobiles become more electronics intensive, in terms of electronic accessories and sophistication of control systems, the need becomes greater for increased electrical supply. As a result, the alternator has become physically larger and more powerful as automotive electrical needs have increased.
In addition, the need for increasing operating efficiencies from I.C. engines mandates a powerful and frequently operated starter motor to resume I.C. engine operation on short demand cycles. And, while these separate trends have been in place, a third element always present in automotive design, is packaging efficiency in terms of underhood space. As these trends have progressed, a commonly proposed strategy is to combine the starter and alternator/generator into a single underhood element. In this regard, the starter function of the starter/alternator can be quite powerful vis-à-vis the I.C. engine being started inasmuch as the I.C. engine is required to achieve self-sustaining operation within xc2xd to 1 second of starter initiation. This design circumstance of a relatively powerful starter function vis-à-vis the IC engine can lead to results that are potentially undesirable. For example, in the circumstance where the I.C. fails to run of its own accord once the starter has engaged to start the I.C. engine, the starter may run in an overspeed condition and itself fail owing to the heat generated in the starter windings owing to the overspeed condition. In addition, other components in the starter/alternator system, i.e., battery and wiring to the starter, supporting circuits, and fusing may be used beyond design capacity if the non-starting I.C. engine condition is not detected, diagnosed, and instead is allowed to persist beyond a predetermined threshold.
The present invention is directed to solving at least one of the potential problems is associated with the trend towards combined starter and generator/alternator functions and short demand cycle I.C. engine operation. Specifically, the present invention proposes a method of sensing and diagnosing a non-starting condition where an I.C. engine start sequence is initiated and the I.C. engine fails to operate in a self sustaining manner. The non-starting condition can be sensed either directly from a rotation and/or position sensor mounted to the starter/alternator or, alternatively, the condition can be sensed from another I.C. engine driven accessory similarly equipped with a rotation and/or speed sensor or, most preferably, directly from the crank or cam position sensor on the I.C. engine itself. If an engine driven accessory is being checked, such an accessory may include, but not be limited to, an engine driven cooling fan, the waterpump, A/C compressor, or power steering pump.